This invention relates to a filter flow indicator for an aquarium filter, and more particularly to a flow indicator for an aerobic aquarium filter which indicates when the filter bag needs replacement.
Whenever aquatic animals are to be maintained within an aquarium environment, the quality of the water in which they live must be maintained at a suitable level. In addition to properly controlling the temperature, the toxic material content of the water must be maintained at a sufficiently low level to prevent harm to the aquatic animals, which are primarily fish.
To combat the problem of toxic waste build-up, three types of filtration are used. The first is physical filtration wherein a water permeable membrane structure traps suspended waste material as contaminated water passes through the membrane. The second is chemical filtration which generally uses activated carbon and ion exchange resins to deactivate mostly organic waste. The third is biological filtration which is accomplished by means of living organisms such as bacteria which, among other thing, rid the aquarium of ammonia.
One example of a highly effective filter which provides physical, chemical and aerobic filtration is described in U.S. Pat. No. 4,622,148 assigned to the assignee of the present invention. The filter is in the form of an enclosed filter bag, pouch or receptacle into which a continuous supply of contaminated water flows.
The filter bag has walls which are made at least partially of a porous filter membrane. The bag is open at one end into which contaminated water is pumped. The contaminated water which flows into the bag exits through the porous walls of the bag. As the filter walls clog with contaminants, the flow of water through the walls will eventually slow down and stop.
The filter bag shown in the patent is constructed so that as the contaminants clog the filter walls, the fibrous material expands to permit the water flow to continue through the walls. The expanding action provides a longer lasting aerobic filter, but ultimately, the filter will clog and will substantially reduce any flow of water therethrough.
When using a filter bag in which the water passes transversely through the filter, when the filter clogs the water will flow over the filter indicating a clogged bag. However, with an aerobic filter as described wherein the water flows into the bag and then outward through the walls, it is not readily visible when the flow rate is reduced. If one neglects to change the bag at a predetermined time interval, the filtering action may have slowed to a point where the toxic contaminants are building up in the aquarium and will harm the fish.
A flow indicator for the filter bag which indicates when the bag should be replaced would be very beneficial. It would be particularly beneficial if it clearly indicates that a replacement is necessary before the flow through the bag completely stops so as to assure replacement before a build up of toxic chemicals in the aquarium.